There are many examples where damage of peripheral nerve caused by accident or the like is unable to be completely restored. There are also many clinical examples where peripheral nerve must be excised as a result of surgical operations in general. In the damage of peripheral nerves, autologous nerve grafting has been an only means besides a direct anastomosis. However, the result thereof is not always satisfactory but recovery of sensory perception and capacity for locomotion are bad and the aftereffect due to erroneous governing is noted as well. In addition, there are many patients complaining not only the aftereffect such as pain and deficiency in sensory perception but also the abnormal sensory perception of the diseased area or, particularly, pain.
An attempt for the regeneration of nerve by connection of gaps of peripheral nerve using a connecting tube made of artificial materials has been briskly carried out since early 1980's. However, all of the studies of connecting channels using non-absorptive synthetic artificial materials have resulted in failure. In order to solve the above, it is necessary to consider in the followings such as that invasion of connective tissues from outside is prevented during the regeneration of nerve bundles, that substance interchange inside and outside the channels or neogenesis of capillary blood vessels in channel walls is necessary, that a substance acting as a scaffold suitable for the growth of Schwann cells and axon in the channel is necessary and that, after the regeneration, the used material is degraded and absorbed. Taking those conditions into consideration, studies for artificial nerve connecting tube by a biodegradable and bioabsorbable material have been carried out thereafter.
With regard to the regeneration of peripheral nerve, attempts for extending the distance between the stumps which are able to be regenerated using a silicone tube have been conducted since a silicone tube model was reported in 1982. However, since nutrients are unable to permeate through the wall of silicone tube, there is a problem such as that the nutrients are not sufficiently provided to nerve axon whereby capillary blood vessel is unable to be produced in silicone and no satisfactory nerve regeneration has been available even when a silicone tube is used. Further, even if the nerve is able to be regenerated, there is a problem that the silicone tube which is a foreign substance anyway must be removed by means of further surgical operation, etc.
On the other hand, regeneration of peripheral nerve using a tube comprising a biodegradable polymer in place of a silicone tube has been attempted. When a nerve regeneration tube comprising a biodegradable polymer is used, the nerve regeneration tube is gradually degraded and absorbed in vivo by hydrolysis or by the action of enzymes after the nerve is regenerated whereby there is no need of taking out it by a means such as further surgical operation.
With regard to a nerve regeneration tube comprising a biodegradable polymer as such, there is a disclosure in, for example the Patent Document 1, for an auxiliary material for nerve regeneration wherein a polyester mantle in a blade form is filled with bundles of collagen fiber on which laminin and fibronectin are coated. In the Patent Document 2, there is a disclosure for an artificial nerve tube which comprises a tubular body comprising polyglycolic acid and, in the lumen of the tubular body, a collagen body having gaps and penetrating the tubular body nearly in parallel to the axial line of said tubular body where the gap is filled with a matrix gel containing collagen, laminin, etc. In the Patent Document 3, there is a disclosure for an artificial nerve tube which comprises a tubular body comprising polyglycolic acid and laminin-coated collagen fiber bundles inserted into the lumen of the tubular body nearly in parallel to the axial line of the tubular body. In the Patent Document 4, there is a disclosure for an instrument for the regeneration of biotissues or organs formed by such a manner that bundles of collagen fiber are inserted into the lumen of tubular body made of collagen together with a collagen solution. Further, in the Patent Document 5, there is a disclosure for a nerve regeneration tube where collagen is coated on and impregnated into the inner side and sponge part of a tubular body in which the inner layer has sponge of a lactic acid/ε-caprolactone copolymer while the outer layer has a reinforcing material comprising a braided rope of polylactic acid.
Those nerve regeneration tubes as such are manufactured in such a manner that a biodegradable polymer is applied on the outer surface of a tubular body prepared by using ultrafine fiber comprising a sole biodegradable polymer and a biodegradable polymer is further filled in the inner side of the tubular body. However, since the degrading speed of the biodegradable polymer which is a material for constituting the tubular body is too quick or too slow, there are problems such as that they are unable to be used for the connection of nerve with a relatively long gap (about 40 mm or longer), that the nerve regeneration tube is not degraded/absorbed but remains even after the connection of nerve and that strength, flexibility, etc. in practical use are not satisfactory.
(Patent Documents)
1. Japanese Patent Application Laid-Open (JP-A) No. 237139/93
2. WO 98/22155
3. WO 99/63908
4. Japanese Patent Application Laid-Open (JP-A) No. 2002-320630
5. Japanese Patent Application Laid-Open (JP-A) No. 2003-19196